The present invention relates to the packaging of integrated circuits (ICs) and more particularly to a mold and a substrate for use in a center gate molding operation.
At present, a number of different molds for center gate molding applications are available in the market. These include air vents for releasing air which is driven out of the mold cavity during the molding operation. Certain air vent designs include air vent holes which are through-holes extending through one of the mold parts.
However, molds with air vent holes require frequent cleaning, for instance, once every six hundred mold shots. The requirement for frequent cleaning makes such molds impractical for use in mass production.
Other mold designs do not include air vent holes but instead are either provided with small air vent reliefs in between solder pad areas or a full relief area around the mold cavity. However, provision of small air vent reliefs in between solder pad areas increases the risk of resin bleed onto solder pads in the event of solder pad offset arising from lapses in substrate manufacturing precision. On the other hand, provision of a full relief area around the mold cavity reduces the substrate area available for clamping and consequently increases the incidence of solder mask cracks due to the increased clamping pressure experienced by the substrate arising from application of the same clamping force on a smaller clamping area.
Furthermore, current substrate designs for center gate molded ball grid array (BGA) packages are susceptible to resin bleed and thus often fail the visual inspection criteria.
In view of the foregoing, a need exists for a mold and a substrate that improve center gate molding process robustness and resultant package reliability, and that can be used for mass production.